Organic light emitting display device and method of manufacturing the same

ABSTRACT

Discussed is an organic light emitting display device. The organic light emitting display device includes a substrate in which red, green, and blue pixel areas are defined, a first electrode and a first hole transporting layer that are formed on the substrate, first to third emission common layers formed in each of the pixel areas on the first hole transporting layer, and an electron transporting layer and a second electrode that are formed on the third emission common layer. Accordingly, color mixture is prevented, limitations due to a defective mask are overcome, a process is simplified, and the manufacturing cost is saved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the Korean Patent Application No.10-2012-0121726 filed on Oct. 31, 2012, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND

1. Field of the Invention

The present invention relates to an organic light emitting displaydevice and a method of manufacturing the same.

2. Discussion of the Related Art

As a type of new flat panel display device, organic light emittingdisplay devices are self-emitting display devices, and have a betterviewing angle and contrast ratio than liquid crystal display (LCD)devices. Also, since the organic light emitting display devices do notneed a separate backlight, it is possible to lighten and thin theorganic light emitting display devices, and the organic light emittingdisplay devices have excellent power consumption compared to LCD devicesand the other flat panel display devices. Furthermore, the organic lightemitting display devices are driven with a low direct current (DC)voltage, have a fast response time, and are low in manufacturing cost.

In organic light emitting display devices, an electron and a hole arerespectively injected from a cathode and an anode into an emittingmaterial layer, and, when an exciton in which the injected electron andhole are combined is shifted from an excited state to a base state,light is emitted. In this case, the types of organic light emittingdisplay devices are categorized into a top emission type, a bottomemission type, and a dual emission type according to an emissiondirection of light, and categorized into a passive matrix type and anactive matrix type according to a driving type.

Specifically, the organic light emitting display devices includes afirst electrode (anode), a hole transporting layer, an emitting materiallayer including a red organic emission pattern, a green organic emissionpattern, and a blue organic emission pattern, an electron transportinglayer, and a second electrode (cathode), which are formed in each of ared pixel area (Rp), a green pixel area (Rg), and a blue pixel area(Rb).

In the organic light emitting display devices having the configuration,when a voltage is applied to the first and second electrodes, a holemoves to the emitting material layer through the hole transportinglayer, an electron moves to the emitting material layer through theelectron transporting layer, and the hole and the electron are combinedin the emitting material layer, thereby emitting light.

In the organic light emitting display devices, a fine metal mask (FMM)process is used for patterning the emitting material layer between twoelectrodes disposed on a substrate.

However, due to limitations of mask manufacturing technology, it isdifficult to apply the FMM process to a large size and high resolution.That is, when the organic light emitting display device is applied to alarge area, a mask sags due to the weight thereof, and thus, it isdifficult to form a desired pattern. Also, the spread of organicmaterials increases due to a separated distance between the mask and adeposition portion, and therefore, it is difficult to realize highresolution.

For this reason, various methods of manufacturing a high-resolutionorganic light emitting display device are required.

SUMMARY

Accordingly, the present invention is directed to an organic lightemitting display device and a method of manufacturing the same thatsubstantially obviate one or more problems due to limitations anddisadvantages of the related art.

An aspect of the present invention is directed to an high-resolutionorganic light emitting display device for realizing excellent lightoutput efficiency, maintaining color characteristic, simplifying aprocess, and saving the manufacturing cost.

Additional advantages and features of the invention will be set forth inpart in the description which follows and in part will become apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from practice of the invention. Theobjectives and other advantages of the invention may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, there isprovided an organic light emitting display device including: asubstrate, red, green, and blue pixel areas being defined in thesubstrate; a first electrode and a first hole transporting layer thatare formed on the substrate; first to third emission common layersformed in each of the pixel areas, on the first hole transporting layer;and an electron transporting layer and a second electrode that areformed on the third emission common layer.

In another aspect of the present invention, there is provided a methodof manufacturing an organic light emitting display device whichincludes: forming a first electrode over a substrate in which red,green, and blue pixel areas are defined; forming a first holetransporting layer on the first electrode; forming a second holetransporting layer on the first hole transporting layer in a positioncorresponding to the red pixel area; forming a first emission commonlayer on the second hole transporting layer and the first holetransporting layer in respective positions corresponding to the greenand blue pixel areas; forming a third hole transporting layer on thefirst emission common layer in a position corresponding to the greenpixel area; forming a second emission common layer on the third holetransporting layer and the first emission common layer in respectivepositions corresponding to the red and blue pixel areas; forming afourth hole transporting layer on the second emission common layer in aposition corresponding to the blue pixel area; forming a third emissioncommon layer on the fourth hole transporting layer and the secondemission common layer in respective positions corresponding to the redand green pixel areas; forming an electron transporting layer on thethird emission common layer; and forming a second electrode on theelectron transporting layer.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a sectional view schematically illustrating an organic lightemitting display device according to an embodiment of the presentinvention;

FIG. 2 is a view showing comparison of emission spectrums of respectiveorganic light emitting display devices according to a comparativeexample and an embodiment; and

FIGS. 3 to 5 are views showing comparison of efficient characteristics(cd/A) with respect to luminance (cd/m²) of respective organic lightemitting display devices according to a comparative example and anembodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Like referencenumerals refer to like elements throughout. In the followingdescription, when the detailed description of the relevant knownfunction or configuration is determined to unnecessarily obscure theimportant point of the present invention, the detailed description isnot provided.

FIG. 1 is a sectional view schematically illustrating an organic lightemitting display device according to an embodiment of the presentinvention.

As illustrated in FIG. 1, the organic light emitting display deviceincludes a first electrode (anode) 110, a hole injection layer 120, afirst hole transporting layer 130, a second hole transporting layer 132,a third hole transporting layer 134, a fourth hole transporting layer136, an emitting material layer 140 including first to third emissioncommon layers 142, 144 and 146, an electron transporting layer 150, asecond electrode (cathode) 160, and a capping layer 170 that are stackedon a substrate (not shown) in which a red pixel Rp, a green pixel areaGp, and a blue pixel area Bp are defined.

Although not shown, in the organic light emitting display device, aplurality of gate lines and a plurality of data lines, which define aplurality of pixel areas Rp, Gp, and Bp by intersections therebetween,and a plurality of power lines that are extended in parallel torespective corresponding lines among the gate lines and the data linesare disposed on the substrate (not shown). A switching thin filmtransistor (TFT) connected to a corresponding gate line and data lineand a driving TFT connected to the switching TFT are disposed in each ofthe pixel areas Rp, Gp, and Bp. Here, the driving TFT is connected tothe first electrode 110.

In an embodiment, the organic light emitting display device includes anorganic layer between the first electrode 110 and the second electrode160 facing the first electrode 110. The organic layer includes the holeinjection layer 120, the first hole transporting layer 130, the secondhole transporting layer 132, the third hole transporting layer 134, thefourth hole transporting layer 136, the emitting material layer 140including the first to third emission common layers 142, 144 and 146,and the electron transporting layer 150. Here, the first emission commonlayer 142 may be formed of a red organic material, the second emissioncommon layer 144 may be formed of a green organic material, and thethird emission common layer 146 may be formed of a blue organicmaterial.

The first electrode 110 is formed in a plate shape in the red pixel areaRp, the green pixel area Gp, and the blue pixel area Bp, on thesubstrate (not shown). The first electrode 110 is a reflectiveelectrode, and for example, may have a multi-layer structure thatincludes a transparent conductive material layer (having a high workfunction) such as indium tin oxide (ITO) and a reflective material layersuch as Ag or an Ag alloy.

The hole injection layer 120 and the first hole transporting layer 130are formed on the first electrode 110 in respective positionscorresponding to the red pixel area Rp, the green pixel area Gp, and theblue pixel area Bp. The first hole transporting layer 130 may be calleda common layer, and the hole injection layer 120 may not be provided. Athickness of the hole injection layer 120 and first hole transportinglayer 130 may be about 100 Å to about 600 Å, but may be adjusted inconsideration of hole injection characteristic and hole transportcharacteristic.

The second hole transporting layer 132 is formed on the first holetransporting layer 130 in a position corresponding to the red pixel areaRp. That is, the second hole transporting layer 132 is formed betweenthe first hole transporting layer 130 and the first emission commonlayer 142. A thickness of the second hole transporting layer 132 may beabout 100 Å to about 1100 Å, but may be adjusted in consideration ofhole transport characteristic. Alternatively, the second holetransporting layer 132 may not be provided.

The third hole transporting layer 134 is formed on the first emissioncommon layer 142 in a position corresponding to the green pixel area Gp.That is, the third hole transporting layer 134 is formed between thefirst emission common layer 142 and the second emission common layer144. A thickness of the third hole transporting layer 134 may be about100 Å to about 750 Å, but may be adjusted in consideration of holetransport characteristic. Alternatively, the third hole transportinglayer 134 may not be provided.

The fourth hole transporting layer 136 is formed on the second emissioncommon layer 144 in a position corresponding to the blue pixel area Bp.That is, the fourth hole transporting layer 136 is formed between thesecond emission common layer 144 and the third emission common layer146. A thickness of the fourth hole transporting layer 136 may be about100 Å to about 400 Å, but may be adjusted in consideration of holetransport characteristic. Alternatively, the fourth hole transportinglayer 136 may not be provided.

In an embodiment, a thickness of the third transporting layer 134 may beless than that of the second hole transporting layer 132 and greaterthan that of the fourth hole transporting layer 136, but the spirit andscope of the present invention are not limited thereto.

The emitting material layer 140 is formed in respective positionscorresponding to the red pixel area Rp, the green pixel area Gp, and theblue pixel area Bp. That is, an emitting material layer 140 is formed asa common layer in each pixel area, and thus, the emitting material layer140 may be formed even without an FMM.

In an embodiment, the first emission common layer 142 is formed on thesecond hole transporting layer 132 and the first hole transporting layer130 that is disposed in respective positions corresponding to the greenand blue pixel areas Gp and Bp. The second emission common layer 144 isformed on the third hole transporting layer 134 and the first emissioncommon layer 142 that is disposed in respective positions correspondingto the red and blue pixel areas Rp and Bp. The third emission commonlayer 146 is formed on the fourth hole transporting layer 136 and thesecond emission common layer 144 that is disposed in respectivepositions corresponding to the red and green pixel areas Rp and Gp.

The first to third emission common layers 142, 144 and 146 may be formedto have the same thickness. For example, the thickness of each of thefirst to third emission common layers 142, 144 and 146 may be about 100Å to about 400 Å, but may be adjusted in consideration of emissioncharacteristic.

The electron transporting layer 150 is formed on the third emissioncommon layer 146 in respective positions corresponding to the red pixelarea Rp, the green pixel area Gp, and thus may be called a common layer.A thickness of the electron transporting layer 150 may be about 250 Å toabout 350 Å, but may be adjusted in consideration of electron transportcharacteristic. The electron transporting layer 150 may act as anelectron transport and injection layer, but an electron injection layermay be separately formed on the electron transporting layer 150.

The second electrode 160 is formed on the electron transporting layer150. For example, the second electrode 160 is formed of an alloy (Mg:Ag)of Mg and Ag, and has semi-transmissive characteristic. That is, lightemitted from the emitting material layer 140 is transferred to theoutside through the second electrode 160, in which case some of thelight is again transferred to the first electrode 110 because the secondelectrode 160 has semi-transmissive characteristic.

Therefore, repetitive reflection is performed between the firstelectrode 110 (acting as a reflective electrode) and the secondelectrode 160. This is called the micro-cavity effect. That is, light isrepeatedly reflected in a cavity between an anode (which is the firstelectrode 110) and a cathode that is the second electrode 160, therebyincreasing light efficiency.

In this case, light respectively emitted from the first to thirdemission common layers 142, 144 and 146 has different wavelengths, andthus, a thickness “d” of a cavity defined as a distance between thefirst and second electrodes 110 and 160 is differently set. That is, thethickness “d” of the green pixel area Gp is less than that of the redpixel area Rp that emits red light having the longest wavelength, andgreater than that of the blue pixel area Bp that emits blue light havingthe shortest wavelength.

In the present invention, therefore, distances between the first andsecond electrodes 110 and 160 are differently formed by adjusting therespective thicknesses of the second to fourth hole transporting layers132, 134 and 136. That is, the thickness of the third hole transportinglayer 134 is less than that of the second hole transporting layer 132,and greater than that of the fourth hole transporting layer 136.

The capping layer 170 increases a light extraction effect, and may beformed of one of materials of the first to fourth hole transportinglayers 130, 132, 134 and 136, a material of the electron transportinglayer 150, and host materials of the red, green, and blue emissioncommon layers 142, 144 and 146. Alternatively, the capping layer 170 maynot be provided.

As described above, the organic light emitting display device accordingto an embodiment of the present invention maintains light outputefficiency and color characteristic, and simultaneously realizes ahigh-quality image.

However, the FMM having an opening is used in correspondence with eachpixel area, forming a material pattern in each of the pixel areas Rp, Gpand Bp. In this case, a process using the FMM is needed in a separatechamber, for forming the second to fourth hole transporting layers 132,134 and 136 having different thicknesses.

First, the first electrode 110 is formed, and then, the hole injectionlayer 120 and the first hole transporting layer 130 are formed withoutthe FMM in a first chamber. In the hole injection layer 120, a P-typedopant, for example, boron (B) may be doped into the material of thefirst hole transporting layer 130.

Subsequently, the second hole transporting layer 132 is formed in thered pixel area Rp by using a first FMM in a second chamber. In thesecond hole transporting layer 132, a P-type dopant, for example, boron(B) may be doped into the material of the first hole transporting layer130.

Subsequently, the first emission common layer 142 is formed of a redorganic material without the FMM in a third chamber.

Subsequently, the third hole transporting layer 134 is formed in thegreen pixel area Gp by using a second FMM in a fourth chamber. In thethird hole transporting layer 134, a P-type dopant, for example, boron(B) may be doped into the material of the first hole transporting layer130.

Subsequently, the second emission common layer 144 is formed of a redorganic material without the FMM in a fifth chamber.

Subsequently, the fourth hole transporting layer 136 is formed in theblue pixel area Bp by using a third FMM in a sixth chamber. In thefourth hole transporting layer 136, a P-type dopant, for example, boron(B) may be doped into the material of the first hole transporting layer130.

Subsequently, the third emission common layer 146 is formed of a blueorganic material without the FMM in a seventh chamber.

Finally, the electron transporting layer 150, the second electrode 160,and the capping layer 170 are sequentially formed without the FMM ineighth to tenth chambers, respectively.

That is, a process may be performed using only three FMMs in a total often chambers, for implementing the micro-cavity structure.

As described above, the organic light emitting display device accordingto an embodiment of the present invention can solve problems due to adefective mask, simplify a process, and save the manufacturing cost.

FIG. 2 and Table 1 show comparison of emission spectrums of respectiveorganic light emitting display devices according to a comparativeexample and an embodiment.

TABLE 1 Result Division Intensity CIE_x CIE_y Red (R) Comparativeexample 1 0.658 0.340 Embodiment 0.98 0.659 0.339 Green (G) Comparativeexample 1 0.257 0.710 Embodiment 1.02 0.259 0.709 Blue (B) Comparativeexample 1 0.138 0.056 Embodiment 0.99 0.139 0.056

As shown in FIG. 2 and Table 1, it can be seen that the comparativeexample and an embodiment hardly have a color characteristic differencein emission spectrums in respective pixel areas Rp, Gp and Bp.

Here, the comparative example (illustrated as a dotted line) denotes acase in which a red emission layer, a green emission layer, and a blueemission layer are stacked as a single layer in each pixel area, and anembodiment (illustrated as a solid line) denotes a structure accordingto an embodiment of the present invention. That is, the structure is astructure in which the red, green, and blue emission layers are allincluded in each pixel area, in which case the red, green, and blueemission layers are sequentially stacked trebly in the red pixel areaRp, the green and blue emission layers are sequentially stacked doublyin the green pixel area Gp, and the red and green emission layers aresequentially stacked doubly in the blue pixel area Bp.

In this case, an energy band gap of the green emission layer is greaterthan that of the red emission layer, and less than that of the blueemission layer. That is, an electron and a hole are first combined toemit light in a layer having a broad energy band gap, and then, when anelectron and a hole are again combined in a layer having an energy bandgap narrower than the broad energy band gap, light may be emitted.However, an electron and a hole are first combined to emit light in alayer having a narrow energy band gap, and then, when an electron and ahole are again combined in a layer having an energy band gap broaderthan the narrow energy band gap, light cannot be emitted.

Therefore, as in the red pixel area Rp of FIG. 1, in a structure inwhich the red, green, and blue emission layers are sequentially stackedbetween the first and second electrodes 110 and 160, an electron and ahole are combined to emit light in the red emission layer, and then,light is not emitted from the green and blue emission layers.

Moreover, as in the green pixel area Gp of FIG. 1, in a structure inwhich the green and blue emission layers are sequentially stackedbetween the first and second electrodes 110 and 160, an electron and ahole are combined to emit light in the green emission layer, and then,light is not emitted from the blue emission layer having a broad energyband gap.

FIGS. 3 to 5 are views showing comparison of efficient characteristics(cd/A) with respect to luminance (cd/m²) of respective organic lightemitting display devices according to a comparative example and anembodiment. Here, FIG. 3 shows comparison of efficient characteristics(cd/A) with respect to luminance (cd/m²) in the red pixel area, FIG. 4shows comparison of efficient characteristics (cd/A) with respect toluminance (cd/m²) in the green pixel area, and FIG. 5 shows comparisonof efficient characteristics (cd/A) with respect to luminance (cd/m²) inthe blue pixel area.

As shown in FIGS. 3 to 5, it can be seen that the comparative exampleand an embodiment hardly have an efficient characteristic difference ineach of the pixel areas Rp, Gp and Bp.

Therefore, the emitting material layer is stacked as the red, green, orblue emission common layer, but the organic light emitting displaydevice according to an embodiment of the present invention can maintaincolor characteristic and realize a high-quality image.

In the specification, a top emission type of organic light emittingdisplay device including a plurality of organic light emitting diodes(OLEDs) has been exemplified, but the spirit and scope of the presentinvention are not limited thereto. The present invention may be appliedto organic light emitting display devices having various types such as abottom emission type, a dual emission type, a tandem type, etc.

According to the present invention, although the red, green, and blueemission layers are formed as the common layers in the red, green, andblue pixel areas, light output efficiency is excellent, and colorcharacteristic is maintained. Also, it is not required to form aseparate emitting material layer in each pixel area, and thus, theemitting material layer is formed without using an FMM. Accordingly,color mixture is prevented, limitations due to a defective mask areovercome, a process is simplified, and the manufacturing cost is saved.

Therefore, the organic light emitting display device according to thepresent invention can realize high resolution.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic light emitting display device,comprising: a substrate, red, green, and blue pixel areas being definedin the substrate; a first electrode and a first hole transporting layerthat are formed on the substrate; first to third emission common layersformed in each of the pixel areas, on the first hole transporting layer;and an electron transporting layer and a second electrode that areformed on the third emission common layer.
 2. The organic light emittingdisplay device of claim 1, further comprising: a second holetransporting layer disposed in correspondence with the red pixel area,and formed between the first hole transporting layer and the firstemission common layer; a third hole transporting layer disposed incorrespondence with the green pixel area, and formed between the firstand second emission common layers; and a fourth hole transporting layerdisposed in correspondence with the blue pixel area, and formed betweenthe second and third emission common layers.
 3. The organic lightemitting display device of claim 1, further comprising a hole injectionlayer formed between the first electrode and the first hole transportinglayer.
 4. The organic light emitting display device of claim 2, whereina thickness of the third hole transporting layer is less than athickness of the second hole transporting layer, and greater than athickness of the fourth hole transporting layer.
 5. The organic lightemitting display device of claim 2, wherein each of the second to fourthhole transporting layers is formed by doping a P-type dopant into amaterial forming the first hole transport layer.
 6. The organic lightemitting display device of claim 1, wherein the first electrode is areflective electrode comprising an Ag alloy.
 7. The organic lightemitting display device of claim 1, wherein, the first electrode is areflective electrode, and the second electrode has semi-transmissivecharacteristic.
 8. A method of manufacturing an organic light emittingdisplay device, comprising: forming a first electrode over a substratein which red, green, and blue pixel areas are defined; forming a firsthole transporting layer on the first electrode; forming a second holetransporting layer on the first hole transporting layer in a positioncorresponding to the red pixel area; forming a first emission commonlayer on the second hole transporting layer and the first holetransporting layer in respective positions corresponding to the greenand blue pixel areas; forming a third hole transporting layer on thefirst emission common layer in a position corresponding to the greenpixel area; forming a second emission common layer on the third holetransporting layer and the first emission common layer in respectivepositions corresponding to the red and blue pixel areas; forming afourth hole transporting layer on the second emission common layer in aposition corresponding to the blue pixel area; forming a third emissioncommon layer on the fourth hole transporting layer and the secondemission common layer in respective positions corresponding to the redand green pixel areas; forming an electron transporting layer on thethird emission common layer; and forming a second electrode on theelectron transporting layer.
 9. The method of claim 8, furthercomprising forming, before the forming of a first hole transportinglayer, a hole injection layer on the first electrode.
 10. The method ofclaim 8, wherein a thickness of the third hole transporting layer isless than a thickness of the second hole transporting layer, and greaterthan a thickness of the fourth hole transporting layer.
 11. The methodof claim 8, wherein the first electrode is a reflective electrodecomprising an Ag alloy.
 12. The method of claim 8, wherein each of thesecond to fourth hole transporting layers is formed by doping a P-typedopant into a material forming the first hole transport layer.
 13. Themethod of claim 8, wherein, the first electrode is a reflectiveelectrode, and the second electrode has semi-transmissivecharacteristic.